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How do scientists know how acoustics work? (piefed.social)

submitted 5 days ago by breb@piefed.social to c/askphysics@lemmy.world

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I've seen lot of theory about how it works.
But how do they get to that conclusion?
As far a i know, you can see that it's air vibrating bc when there's a loud noise you can feel the floor vibrating or if i drop something in a table and i place my hand on it i can feel the table vibrating as well. But how do they know it in more detail. How do they know about the pith and that it's a wave?

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[–] Admetus@sopuli.xyz 1 points 5 days ago* (last edited 5 days ago) (1 children)

Virtually everything scientists know about sound began with microphones which output a voltage wave with the same 'pitch' as the sound wave, and the piezoelectric transducer which enabled extremely sensitive measurements. It's a deep rabbit hole I expect if we go into much detail.

It certainly helped when the cathode-ray tube was able to trace the waves visually in real time.

[–] hildegarde@lemmy.blahaj.zone 9 points 5 days ago (2 children)

absolute nonsense

In the 6th century BCE Pythagoras accurately described the overtone series. Aristotle understood that sound was a pressure wave in the air. In the 1st century CE roman architects were designing music halls around their acoustics.

The field started being much more active during the Renaissance and onward. Most of the big names in the field of acoustics predate the invention of microphones.

[–] Admetus@sopuli.xyz 1 points 5 days ago (1 children)

I get that, but OP wants to know HOW they knew it was a wave, and I only have modern examples that show the 'how'. If you can expand on how Pythagoras 'knew' or 'demonstrated' it was a wave, you should add that to your reply lol.

[–] hildegarde@lemmy.blahaj.zone 1 points 5 days ago (1 children)

The point of my reply was to debunk what you said. I've not read that text and I am no expert. I can only speculate.

If you know that sound is caused by something vibrating, as was known, and you also know that when something moves through air it pushes the air away, you can reasonably conclude that sound is a vibration in the air caused by a vibration in an object.

But I don't know how he came to that conclusion, or what, of any he ran experiments he ran to show it.

My point is that anyone saying you need a microphone to learn about acoustics are talking nonsense. You have to already understand acoustics to even build the first microphone.

[–] Admetus@sopuli.xyz 2 points 5 days ago

I gotcha. I have a bedroom which resonates at a certain frequency of my voice, and it could be compared to the resonance of a wave when you get the driving frequency just right. I didn't need a microphone to quickly realise this from my knowledge, but the ancients were extremely well-versed or understanding of it without using current modern terms or techniques.

[–] breb@piefed.social 1 points 5 days ago (1 children)

how did Aristotle know it was pressure wave in the air? Did he say any reason for that

[–] iii@mander.xyz 1 points 4 days ago* (last edited 4 days ago)

At that time it was a hypothesis. But the motion of snares was one of his inspirations.

In any case, it's impossible to "proof" anything in physics, you can only disprove things. If enough people fail to disprove a hypothesis, for a long enough time, a hypothesis is generally accepted as true.

An early experiment that supports the hypothesis, was in the 17th century, when experiments in vacuum became possible. Robert Boyle put a mechanical bell inside a vacuum chamber and, as the bell rang, no sound was transmitted. Highly suggesting that the presence of a medium to transfer the motion is important. (1)

Changing the type or amount of gas changes the pitch, again suggesting the medium is important.